The consensus among palaeontologists is that dinosaurs and birds are so closely related that the only real difference is a pair of wings. From this, I think we can conclude that dinos taste pretty much like turkey, making them a welcome alternative to the traditional Thanksgiving meal if you are expecting a large crowd for the holidays.
First, bag a dinosaur. The truly impressive drumsticks of tyrannosaurus make this the preferred genus. I’ll let you work out the time travel details for yourself, but there are some tips for the hunt itself in the video below. Actually, I think the theropod in the clip is an allosaurus (note the foreclaws), but the same principle applies. Just use a bigger spear.
A good-size tyrannosaur weighs 7.5 tons (6.8 metric), but, after it is field dressed in the same manner as a wild turkey, it is a more manageable 5.
Bring back the dressed tyrannosaur carcass to your backyard. Picnicking in the Cretaceous is not recommended; scavengers of the time are very large and aggressive, and so are apt to be annoying pests. Spitting a beast of this size over an open flame is not really practical, so pit roasting is the way to go. In order to accommodate the tail fully (which, like alligator, is the tastiest morsel), your pit will need to be an oblong 40 feet long by 20 feet wide and 16 deep (12m x 6m x 4.9m). Line with rocks. Start a blazing fire throughout the pit. Allow to burn down until the hot coals fill the pit halfway. Toss in another layer of stones. Push in the tyrannosaur. Cover meat with a mat to keep out dirt; fronds and palm leaves will work for your mat, but to save time you might want to use carpets. Do not use synthetic materials. Cover the matted tyrannosaur with dirt.
Turkeys usually cook 15 minutes per pound. This scales up to 104 days, but, fortunately, cooking times are nonlinear with weight. A whole steer takes only 24 hours, so 48 should be time enough for a dinosaur. Double check with meat thermometer to be sure it is done.
Dig up tyrannosaur and serve. Feeds 2500 guests.