This may depend on whether one is referring to burnt offerings offered by individuals or to those designated as continual burnt offerings. In the case of those presented by individual worshipers, these may well have been offered up all at once even though the animal was divided and washed. In the case of the continual burnt offerings, these seem to have been offered up in portions since, as we are told, the evening offering was required to be offered continually until morning.

The continual burnt offering does not focus on any one individual. This sacrifice was for the continual consecration of the entire nation and was made by the priest alone. Unlike the individual burnt offering where different types of animals were designated to be offered, the continual burnt offering was to always be a one-year old lamb. According to Exodus 29:38-46, this offering was to be accompanied by its meal offering and drink offering every morning and every evening by the priest.

“Now this is what you shall offer on the altar: two one-year old lambs each day, continuously. The one lamb you shall offer in the morning and the other lamb you shall offer at twilight; and there shall be one-tenth of an ephah (a bushel) of fine flour mixed with one-fourth of a hin (about a quart) of beaten oil, and one-fourth of a hin of wine for a drink offering with one lamb.”

“The other lamb you shall offer at twilight and shall offer with it the same grain offering and the same drink offering as in the morning, for a soothing aroma, an offering by fire to the Lord. It shall be a continual burnt offering throughout your generations at the doorway of the tent of meeting before the Lord, where I will meet with you, to speak to you there. I will meet there with the sons of Israel, and it shall be consecrated by My glory. I will consecrate the tent of meeting and the altar; I will also consecrate Aaron and his sons to minister as priests to Me. I will dwell among the sons of Israel and will be their God. They shall know that I am the Lord their God who brought them out of the land of Egypt, that I might dwell among them; I am the Lord their God.”

1. This was intended to serve as a constant reminder and as a renewal of Israel’s consecration to God as a kingdom of priests. It also served to remind Israel of their fellowship with the God who brought them out of Egypt. Israel’s association with God was to always be one of remembrance for God's deliverance. As with the individual burnt offering, atonement was to be secondary.
2. The fire on the altar of burnt offering was never permitted to go out in Israel. God issues this warning three times in chapter six alone, 9, 12, and 13.

“Then the Lord spoke to Moses, saying. ‘Command Aaron and his sons, saying,’ 'This is the law for the burnt offering: the burnt offering itself shall remain on the hearth on the altar all night until the morning, and the fire on the altar is to be kept burning on it.'”

“The priest is to put on his linen robe, and he shall put on undergarments next to his flesh; and he shall take up the ashes to which the fire reduces the burnt offering on the altar and place them beside the altar. Then he shall take off his garments and put on other garments and carry the ashes outside the camp to a clean place. The fire on the altar shall be kept burning on it. It shall not go out, but the priest shall burn wood on it every morning; and he shall lay out the burnt offering on it and offer up in smoke the fat portions of the peace offerings on it. Fire shall be kept burning continually on the altar; it is not to go out.”

The fire was not to be allowed to go out nor was fire from any other source permitted to be placed upon the altar. This was the sin of Nadab and Abihu. To allow the fire to go out would indicate neglect of holy things by the priest. It would also suggest that Israel had forgotten its God. For Israel, worship was not to be simply an occasional informal exercise. Worship was to be a continual process of life in Israel.

3. The ashes of this offering were to remain on the altar from the evening sacrifice until the morning sacrifice. It would seem that the priests would offer the sacrifice of this offering piece by piece throughout the day and night so that the offering was continually burning before the Lord. Thus, it was called the “continual” burnt offering. This would of course be interrupted when other appointed sacrifices were required to be offered. When those offerings were completed, the offering of consecration would resume.