You can use oranges in two ways in a brisket marinade -- you either use the flesh or the zest. The juice from the flesh adds a strong zip to brisket marinade. The zest from the skin, or rather oils from the zest, adds a subtle tang. Either way, soaking brisket in an orange-flavored marinade brings out the sweet flavor of the meat.
Using Orange Juice
Slice an orange in half and squeeze the juice into a bowl, removing any seeds. Mix the remaining marinade ingredients, such as herbs, into the juice. Place the brisket in a bowl and pour the marinade over top. Marinate the meat for a few minutes or several hours, depending on how intense you want the flavor.
Using Orange Zest
Wash the orange and peel the colored part of the skin to zest it. Break and squeeze the zests as you place them in the bowl to help release the oils. Mix the other marinade ingredients into the bowl, such as oil and vinegar. Marinate the meat as desired.