In a large skillet add the Israeli/pearl couscous to a dry, hot skillet. Gently stir to prevent burning. After a few minutes, the couscous will start to brown. Do not burn. Not all the couscous will brown & that's ok.
Add the chicken stock, cover, lower heat, and simmer about 15-18 minutes until liquid is absorbed. Remove from heat, cover, and set aside.
In a large, deep skillet, saute the onions until they start to caramelize then add garlic & cook another minute. Add the spinach and cook until wilted. Sprinkle with salt & pepper.
Add the cooked onions, garlic, & spinach to the couscous. Stir well. Cover and set aside until fish is done.
Line a large rimmed baking sheet with a piece of parchment paper or aluminum foil. Turn oven to broil. Once hot, reduce the oven temperature to 425º.
Wash tomatoes then coat them along with the whole cloves of garlic (skin on) with 1-2 Tablespoons of EVOO. Sprinkle with salt. Combine well. Place on a lined baking sheet.
Place baking sheet on the top oven rack and bake for 15-20 minutes at 425ºF, until tomatoes blister & garlic is soft.
Remove from the oven when done. Using a fork or a wooden spoon, smash the garlic. Take half the tomatoes plus the juice and garlic then add to couscous, mixing well.
Just before serving, crumble & add the Feta cheese & Kalamata olives to the couscous and combine.
Using the same rimmed baking sheet, drizzle EVOO and arrange the pieces of cod on the sheet. Sprinkle with garlic powder, salt & pepper, chopped fresh greek oregano. Drizzle lightly with EVOO and place on center rack of 425º oven.
Cook 10-16 minutes, depending on the thickness of cod until it's opaque & flakes.
To serve, place cooked couscous mixture on a serving platter and top with fish fillets. Sprinkle with remaining blistered tomatoes & garlic. Garnish with sprigs of fresh oregano or thyme.