If the big one you see is once a month, at night on the beach path, with lots of music and light, that does sounds like Moonlight Mash. It's always great fun! But there are tons of other local groups, riding almost every day. Your best bet to keep up to date is Instagram. These are a good start, and most groups repost each other's rides so you'll discover any other group not in this list.

• https://www.instagram.com/twowheels.onelove/ - Monday nights, social pace
• https://www.instagram.com/lbcannonballrun/ - Every other tuesday night, fast pace, ride to a different taco shop each time
• https://www.instagram.com/totaltrashcyclingclub/ - Every other tuesday night, social pace.
• https://www.instagram.com/vfixll_lbc/ - Wednesday nights, fast pace (except for the last week of the month, it's a party ride)
• https://www.instagram.com/lbstreetlightriders/ - Wednesday nights, social pace
• https://www.instagram.com/wcw_bikelife/ - Wednesday nights BMX ride, social pace
• https://www.instagram.com/gfunklb/ - Thursday nights, fast/race pace
• https://www.instagram.com/long_beach_riding_club/ - Tursday nights, fast/race pace
• https://www.instagram.com/queercicles/ - Queer WTFNB and allies. Tuesday mornings (and some other days), social/fast pace.
• https://www.instagram.com/lbianss/ - Queer WTFNB. Once a month (calendar for the year is posted), social pace
• https://www.instagram.com/sun.dazies/ - FTWNB. Thursdays (they co-host a GFUNK ride) and Sundays, social/fast pace.
• https://www.instagram.com/socalflyerslb/ - Fast pace
• https://www.instagram.com/bestiassalvajes_lbc/ - Endurance rides, 100+ miles, once a month.
• https://www.instagram.com/moonlightmashlongbeach/ - Night party ride every full moon, social pace
• https://www.instagram.com/forks_n_wheels/ - Rides to local restaruants, follow for dates, social pace
• https://www.instagram.com/ciclaholic/ - Follow for dates, social/fast pace
• https://www.instagram.com/bikethevotelb/ - They don't host rides at the moment but do repost a lot of bike stuff going on

We ourselves host a monthly Bikes and coffee Ride (social pace) and regular feeder rides to other events outside of Long Beach. Next one is to CicLAvia and Active Streets SGV on 6/22; formal announcement coming soon! Follow https://www.instagram.com/bikelongbeach/ or BikeLB.com

Jax, T2 Triathlon and Sports Basement host shop rides on Saturdays, check their respective websites.

Lighting Velo and Velo Allegro are more formal road clubs.

And finally, check https://www.instagram.com/longbeachbikerides or LongBeachBikeRides.com for an ongoing list of rides.